Breakthrough volume, adsorbent collection

Collection of the retention data was initially taken on Tenax and XAD-2 adsorbents at 150, 250, and 350 atmospheres. As experimental work progressed, additional data was taken at closer pressure intervals to better define the trend in breakthrough volume with fluid pressure. Measurement of retention volumes below 100 atmospheres was difficult, due to the "threshold pressure" solubility limit (as defined by the sensitivity of the UV detector) of the test solute probes (23). Most of the generated retention data were measured at three temperatures 40, 60 and 80 C. 

Flow Rate. The effect of flow rate varies with the sorbent. If the flow rate is too high, a nonequilibrium condition occurs due to poor vapor contact, and poor collection efficiency will result. In most cases, once the equilibrium flow rate is reached, no increase in breakthrough volume is observed with reduction in flow rate. In some sorbents, such as silica gel, a high flow rate will cause a heating effect due to adsorbent water. This heating effect may decrease breakthrough volume. 

For accurate results, it is advisable to control the surfactant adsorption performing a titration. The effluent leaving the column is collected until the detector response reaches a plateau corresponding to the absorbance value of the initial surfactant solution. The surfactant concentration in die collected effluent is determined by titration. The missing surfactant mass is adsorbed on the stationary phase in the column. The mass obtained by titration should corroborate the one obtained using the breakthrough volume. 

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